Electrical connections to igniters or electrical supply units



L. GRlFFlTHs 3,041,503

ELECTRICAL CONNECTIONS To ICNTTERS CR ELECTRICAL SUPPLY UNITS June 26, 1962 /A/ VEA/Tof? 5% mw f @N CN 0 H M Q. m N um Sm S S C: NS uw w TTOFP/VEY L. GRIFFITHS June 26,1962

VFiled Nov. s, 1958 2 sheets-shea 2 mw mw om wm Q mm m a mgm w. f

ww S8 S bm vm omm United States Patent O 3,041,503 ELECTRICAL CONNECTIONS TO IGNITERS R ELECTRICAL SUPPLY UNITS Leonard Grlliiths, Coventry, England, assignor to The British Thomson-Houston Company Limited, a British company Iiled Nov. 3, 1958, Ser. No. 771,437 Claims priority, application Great Britain Nov. 5, 1957 6 Claims. (Cl. 317-96) This invention relates to electrical equipment wherein a live or H.T. side of an electrical supply unit is separably electrically connectable with a spark-plug or other ignition device to be energised by said supply unit. The term electrical supply unit as herein used throughout the specification and claims includes high energy igniters (which provide relatively low voltage) high voltage igniters (which provide relatively low energy) such as H.T. magnetos, othodox coil systems and trembler coil systems.

In high energy ignition equipment the igniter may operate at a peak voltage of the order of 2.5 kv. and dissipate energy up to l2 joules or possibly more in the spark discharge.

According to the present invention for an electrical equipment of the 'kind referred to, an electrical connector includes an earthing surface on the electrical `supply unit side of the connector, the earthing surface and a part included in the path through the connector designed for the H.T. being mechanically biased together but separable from one another against the bias by mechanical connection of the connector and the plug or other ignition device or other co-operating part of the equipment with respect to one another and said part included in the H.T. path and said earthing surface being automatically returnable by the bias into contact With one another on disconnection of the connector and thes plug or other ignition device or other co-operating part of the equipment whereby to connect the live `sid-e of the connector to said earthing surface on the electrical supply unit side of said separation.

In practice a lead from the electrical equipment may be separable at more than one location such as at the electrical supply unit and at the spark plug or other ignition device to be energised, in which case the arrangement according to the invention is preferably applied at each of these locations so that at which ever location said lead is disconnected the H.T. path is earthed on the supply side of the separation.

A connector according to the invention may conveniently be used, at the spark plug or other device to be energised, in which case one end of the connector will be connected with a lead from the supply unit and the other end of said connector will be separable yfrom the spark plug or other ignition device.

In one convenient arrangement, the earthing surface being stationary with respect to the connector said part of the electrical path through the connector designed for H.T. comprises a conductive plunger supported for movement in electrical insulation. In another convenient arrangement, the H.T. path through the connector is fixed with respect to the connector and the earthing surface is formed Iby a movable `member surrounding the H.T. path through the connector. The earthing surface may conveniently' be provided by a washer surrounding but radiallyspaced from the H.T. path through the connector.

The casing of the connector may be provided at one end with a cable fixing nut or other lead fixing means for securing a H.T. lead from the supply unit to the connector and also be provided with a part(s) which provide(s) an earthing path between an outside or earthing sheathing of the lead and said earthing surface. The other end Mice of the casing may conveniently be provided with an external thread for securing the connector in a bore in a combustion chamber wall, the connector in this case also serving to secure the spark-plug in the bore in a gas tight manner. I

When the connector is attached to the combustion chamber wall the terminal of the plug moves said part of the path designed for H.T. for example, the plunger and said earthing surface with respect to one another so as to separate them against the bias thereon so that when the connector is unscrewed from the combustion chamber wall said part contacts the earthing surface and automatically earths the H.T. conductor of the lead.

A connector according to the invention may conveniently be built in to the supply unit, in which case said connector may conveniently comprise a movable contact mem-ber through which the H.T. is supplied to the lead from the supply unit and which member is biased so that a portion thereof engages the earthing surface or point but is adapted to be disconnected therefrom by attachment to said unit of a part designed to contact the movable contact member and to provide electrical connection between said contact member and the H.T. conductor of the lead, the disconnection of said part automatically allowing the contact member to connect with the earthing surface so as to earth the H.T. side of the supply unit at said unit.

By these connections at each end of the lead if either end of the lead is disconnected the supply at the disconnected end is automatically earthed. Thus the possibility of an operator contacting a live conductor contact o r terminal is reduced to a minimum removing the risk of shock and in eXtreme cases lethal injury which may arise in high energy ignition or the like equipment where precautions are not taken to prevent operators contacting live conductors, contacts or terminals.

Reference will now be made by way of example to the accompanying drawings in which: Y

FIG. 1 and FIG. 2 are respective half sections of electrical connections at a combusion chamber end and at an an igniter end of the equipment.

FIGS. 3 and 4 are sections of a modification of the connector at the combustion chamber end.

In FIGURE 1 there is shown an electrical connector which makes an electrical connection between an electrical cable or lead 2 and a spark plug 3, which seats on ya sealing Washer 4 in .a bore 4a in a wall `4b of a combustion chamber. A threaded end 1b of a casing or body 1a of the electrical connector is screwedl into a thread 4c in the bore 4a so as to retain the spark-plug in position. The electrical cable 2 comprises la centre conductor 2a which is adapted to carry H.T. from an igniter unit (FIG. 2) and which is surrounded by an earthing sheath 2b separated from the core by insulating material 2c. An end of the electrical cable is received Within a sleeve 5 crimped at 5a on to the sheath of the cable, the latter being located between the sleeve 5 and an inner sleeve 6. The sleeve S has a radi-ally out- Wardly extending flange portion 5b which abu-ts against a radially inwardly extending flange portion 7a of a cable retaining nut which is screwed into an internal thread 8 in the end of the electrical connector. The inner `core 2a of the cable is taken through the end of the electrical connector and within the connector is surrounded by a cable insulator 9 at the inner end of which the core 2a makes electrical connection with a Washer 10.

Electrical connection of lshe H.T. from the Vwasher 10 to a terminal 3a of the spark-plug is made by means of a movable plunger 11, a stem 11a of which is supported in a ceramic or other suitable material insulator 12. In the assembled position, that is with lconnector screwed into the combustion chamber wall as is shown in FIG- URE l, the plunger 11 is pushed towards the cable end of the connector by the terminal 3a of the spark plug against the bias of a spring 13 which is located between the sleeve l6 and an insulating washer 13a abutting the 'end of the insulator 9. By this means a surface 11C of a radial flange portion 11b of the plunger 11 is maintained `separated from a conducting washer 14 which latter is connected with the earthing sheath 2b by means of a retaining sleeve and the casing 1a.

As the electrical connector is unscrewed from the combustion chamber wall, the spring 13 biases the surface 11C into contact with the conducting earthing washer 14 and automatically earths the high tension supply to the plug. Scrcwing the electrical connector back into the combustion chamber wall will automatically break this earthing connection.

In order to assemble the electrical connector the plunger 11, its surrounding insulator 12 and the earthing washer 14 may be assembled as a sub-assembly, one end of the plunger 11 being screwed and/ or riveted or otherwisesecured on to the plunger stem. The unit comprising the plunger 11, its surrounding insulator 12 and the earthing washer 14 may then be inserted in the casing, the position of the insulator 12 being determined in the direction of the plug by means of a shoulder 1c Vin lthe casing 1a of the electrical connector and in the direction of the lead by the retaining sleeve 15. The metal sleeve 15 is next inserted into the connector body 'and thereafter the parts 10; 9; 13a; 13; 5, 6 and 2 are inserted into the connector body and retained in position `iby the -cable fixing nut 7.

Preferably the end of the lead at the supply unit 16 (FIG. 2) is also connected Vthrough an automatically earthing connection. A threaded cylindrical ybush 17 'which is screwed onto an external thread on an inner `cylindrical bush 18 which is secured to a casing 16a of the igniter unit such as by rivets 19a. The end of the 'cable is retained in a sleeve 20 which is crimped on to the cable at 20a. The core of the cable extends within an insulator 21 and is connected at the inner end of the latter with a washer 22. Electrical connection between "the washer 22 and the terminal 16b of the igniter is achieved through a contact 23 carried by Ia spring 24. A spring 13b presses on a washer 13C and biases washer 22 toward contact 23.

if the outer bush 17 is loosened on the inner bush 18 and unscrewed to disconnect the cable from the igniter, the washer 22 moves outwardly and a part 24m of the spring contacts an earthing post provided on the igniter lcasing 16a so Ias to earth the supply lfrom the igniter. The earthing post 25 may be secured in any suitable manner to the casing 16a 'of the igniter. VWhen the 'bush 17 is rescrewed on to che inner bush the :washer 22 pushes on the contact 23 and moves the lpart 24a of the spring member 24 laway from the earthing post 25 to rie-establish the path for the H.T. from the ,igniter through the contact 23, the Washer 22 to the conductor 2a of the lead 2.

In la modified arrangement of the connector at the plug end of the equipment which is illustrated in FIGS. 3 andf4, the end of the lead 2 is received in one end of ferrule 26 and the centre conductor 2a and its insulation 2c extend through the ferrule and the centre conductor is secured by the contact button 27. The earthing surface is movable and formed by a washer 28, of high conductivity material such as brass, behind the Contact buttonrand -biased into contact with the back of the button by a coil spring 29 of square sectioned beryllium bronze acting between the washer 28, to which latter the spring 29 is soldered, and a washer 30 and surrounding ceramic distance sleeve 31. A further coil spring 32 acts between the washer and the ferrule as shown. The ferrule i's Ysurrounded by an internally threaded nut 33 by means of which the connector is mechanically connected on to the threaded end 34 of the plug housing 1a. FIG. 3 shows how the end 34 of the plug housing separates the earthing washer 28 from the back of the contact button 27 when this connection is made and FIG. 4 illustrates that by disconnection of the connector from the plug housing the washer 28 returns into contact with the contact button 27 to provide the Aautomatic earthing of conductor 2a of the lead. An insulating sleeve 35 is provided within `the plug housing as shown.

What I claim is:

l. For an electrical equipment wherein an electrical supply unit for energizing an ignition device is separably electrically connectable through a lead having a supply conductor and an earth conductor with the ignition device to` be energized by said supply unit, an electrical connestor comprising means at one end of the connector for securing the lead to the connector, the other end of said connector being threaded for securing it to the ignition device, a movable earthing surface within the connector, electrically conductive means for directly connecting said earthing surface with the earthing conductor of the lead by a highly conductive electrical connection therewith, an electrically conductive fixed part electrically connected to the supply conductor through said connector, means biasing said fixed part `and said earthing surface directly together, and a cooperating part of the equipment surrounding the ignition device for separating said fixed part and said earthing surface by mechanical connection of said connector and said cooperating part land providing for automatically returning said tixed part and said earthing surface into direct electrical and mechanical connection on disconnection of said connector and cooperating par-t for earthing the supply conductor on the supply unit side of said connector Ifor passing electrical energy from the supply conductor directly to earth.

2. An electrical equipment comprising an electrical supply unit, an ignition device, a lead having a supply conductor and an earth conductor for separably electrically connecting said supply unit to said ignition device, an electrical connector comprising means for securing said lead to the connector, means for securing said connector to said ignition device, an earthing surface within said connector, electrically conductive means for connecting said earthing surface directly -to said earthing conductor of said lead by a highly conductive electrical connection therewith, an electrically conductive part electrically connected to said supply conductor through said connector, and means for biasing said electrically connected part and said earthing surface directly together, a cooperating part of the equipment to which said connector is adapted to be connected, said part and said earthing surface being mechanically separable against the `force of said biasing means by mechanical connection of said connector and said coperating part and automatically returnable into direct electrical and mechanical connection on disconnection of said connector and said cooperating part Ifor earthing the supply conductor on the supply unit side of said connector for passing electrical energy from the supply conductor directly to earth.

3. An electrical equipment comprising an `electrical supply unit, an ignition device, a lead having a supply conductor and an earth conductor for separably electrically connecting said supply unit to said ignition device, an electrical` connector comprising means for securing said lead to the connector, means for securing said connector to said ignition device, a movable electrically conductive member forming an earthing surface within said connector, electrically conductive means for connecting said member directly to said earthing conductor of said lead iby a highly conductive electrical connection therewith, anelectrically conductive part electrically connected to said supply conductor through said connector, and vmeans for biasing said electrically connected part'and said member directly together, a cooperating part of the equipment to which said connector is adapted to be connected, said electrically connected part and said member being mechanically separable against the force of said biasing means by mechanical connection of said connector and said cooperating part and automatically returnable into direct electrical and mechanical connection on disconnection of said connector and said cooperating part for earthing the supply conductor on the supply unit side of said connector for passing electrical energy from the supply conductor directly to earth.

4. An electrical equipment comprising `an electrical supply unit, an ignition device, a lead having a supply conductor and `an earth conductor for separably electrically connecting said supply unit to said ignition device, an electrical connector comprising means yfor securing said lead to the connector, means for securing said connector to said ignition device, an earthing surface within said connector, electrically conductive means for connecting said earthing surface directly to said earthing conductor of said lead by a highly conductive electrical connection therewith, an electrically conductive plunger connected to said supply conductor through said connector, and means for biasing said plunger and said earthing surface together, ya cooperating part of the equipment to `which said connector is adapted to be connected, said plunger and said earthing surface being mechanically separable against the force of said biasing means by mechanical connection of said connector `and said cooperating part and automatically returnable into direct electrical `and mechanical connection on disconnection of said connector and said cooperating part for earthing the supply conductor on the supply unit side of said connector for passing electrical energy from the supply conductor directly to earth.

5. An electrical equipment comprising an electrical supply uni-t, an ignition device, a lead having a supply conductor and an earth conductor -for separably electrically connecting said supply unit to said ignition device, an electrical connector comprising means at one end of said connector for securing said lead to the connector, the other end of said connector being threaded for securing it to said ignition device, means for securing said connector to said ignition device, an earthing surface within said connector, electrically conductive means for connecting said earthing surface directly to said earthing conductor of said lead, by a highly conductive electrical connection therewith, an electrically conductive part electrically connected to said supply conductor through said connector, and means for biasing said electrically connected part and said earthing surface directly together, said electrically connected part and said earthing surface being separable against the force of said biasing means by mechanical connection of said connector and said ignition device and automatically returnable into electrical and mechanical connection on disconnection of said con-nector from said ignition device for earthing the supply conductor on the supply unit side of said connector for passing electrical energy from the supply conductor directly to earth. 6. An electrical equipment comprising an electrical supply unit, an ignition device, a lead having ya supply conductor and an earth conductor for separably electrically connecting said supply unit to said ignition device, an electrical connector comprising means at one end of said connector for securing said lead to the connector, the other end of said connector Ibeing threaded for securing it to said ignition device, means for securing said connector to said ignition device, an earthing surface within said connector, electrically conductive means for connecting said earthing surface directly fto said earthing conduct-or of said lead by a highly conductive electrical connection therewith, an electrically conductive movable part electrically connected to said supply conductor through said connector, insulating means for supporting said movable pant, and means for biasing said movable part and said earthing surface directly together, said mov- -able part and said earthing surface being separable against the Aforce of said biasing means by mechanical connection of said connector and said ignition device and automatically returnable into direct electrical and mechanical connection on disconnection of said connector fromy said ignition device for earthing the supply conductor on the supply unit side of said connector for passing electrical energy from the supply conductor directly to earth.

References Cited in the file of this patent UNITED STATES PATENTS 1,782,745 Rohde Nov. 25, 1930 1,980,488 Kyle etal. Nov. 13, 1934 2,186,038 Peters lan. 9, 1940 2,265,998 Bruno Dec. 16, 1941 2,280,972 Paulson Apr. 28, 1942 2,281,511 Parkin Apr. 28, 1942 2,640,118 Werner May 26, 1953 2,664,475 Harlin Dec. 29, 1953 2,723,364 Cipriani Nov. 8, 1955 

